Air cushioned boat hull



theatre i Weldon hour a aeration at i 1 one.

dppiicatioii @etoher ll, i939, Serial No; t99,iitft 5 (Git-tilin "thisinvention relates to Movement in hoot hull eonrtruetion particularlgapplieahle to a hull oi the eovered in mg Watent lilo. hl itlll, grantedJanuary 1?, will.

*lliie hull has loroud spoon shaped how cape-l hie oi enguiling theaerated water ehurned up log the forefoot so that the vessel rideslargeig upon air hulohles. it has a deadrise or w sheped hottorn, haclroi the lorefoot so that the huhhles m eontinuailg travel up the inclinedsurleew oi the hottom oi the hull and escape at the ehine, which term asused herein refers to the line or angle oi junction hetween the bottomand sides, the purpose losing to prevent the aerated water liow== gg luginto the path oi the propeller, and the hull has a longitudinalsemi-tunnel oi progressive-lg increasing arose-section, beginning git oithat portion oi the hull oi maximum beam into which tunnel the upperpart of the propeller extends,

go the ohiect oi the tunnel being to are up how the depths below thehoat, through the vaeuum produced log forward-movement oi the hull, thecolumn oi solid iuriaerated) water against which the propeller thrusts,avoiding cavitation.

5 The ohlect oi the present invention is the provision oi longitudinalribs or rails located in strategic positions on the bottom oi the hulland accomplishing the lollowins "results:

(a) lo deflect inwardly the spray which go dashes against the how of.the boat go that it will he entrained beneath the hull and not pushedaside hr the displacement of the hull;

(h) To prevent the aerated water thus engulfed, irom going straight backinto the path at oi the propeller;

(cl To prevent the sldewise escape of the aerated water until it reachesthe middle oi the hull;

(d) To permit the lateral escape of the aerated 4 g water in the midshipregion of the hull;

ie) To prevent the aerated water which has escaped at the mids'hipsection, from being drawn haclr under the quarters and into the path ofthe propeller by the vacuum created in the after n region by the passageof the boat through the water, i

Uther obiects oi the invention will appear 'as the following descriptionof a preferred and prac-' tical embodiment thereof proceeds,

50 in the drawing throughout the several figures oi which the samecharacters of reference denote identical parts:

Figure l is a side elevation of a boat hull emhodying the principles ofthe present invention:

g Figure 2 is a bottom plan view: a p

(ml lid-66.5)

Figure l is a trout and view; and

Figures 4 and 5 are sections taken; respectively, along the lines d-iand 5-45 oi higure in Referring now in detail to the several hes,

the numeral i represents in general the hull -which has a broadtransverse how log t, which gives the tread spoon shape to theoverhanging portion i oi the how. The how overhang is slight lg andsmoothly curved at its juncture with the how log t, the curvaturegradually merging into m a deadrlse or ll-shape. Figure 3. shows that adiacent the water line the if-shape at the how is foot and of dissipatingthe most of the air irom gg the water before it reaches the tunnelledportion of the hull; The bubbles continually rise along the inclinedplanes of the V-bottom toward the chines, so that the propeller reactsagainst a Toody of solid, that is to say. unaerated water. go

It happens, however, that at high speeds the hull may overrun theaerated water to such an extent that some of it will reach thepropeller, causing more or less cavitation, and thus putting a limittothe maximum speed.

The present invention provides an outer pair oi rails i and 8 at theforward part of the hull, the front ends 9 and ID of said railsconverging toward the keel line well above the water line on theoverhanging portion of the how. The g rails I and 8 diverge with asmooth curvature so that their rear portions II and I! lie adjacent andpreferably parallel to the chines. The rear ends it and ll of theserails terminate in the mldship region of the hull. M

The function of the forward portions of the rails 1 and 8 is to catchthe frothy portion of the. wave which slides up against the bow, andwhich. ordinarily would be dashed laterally in the form of spray, and totuck it under the forefoot, au'ggg menting the volume ofaerated waterupon which the boat hull glides. The rear or under water portions ofthese rails function to confine the aerated water-beneath the forwardpart of the hullso that practically none of it will be lost or before itreaches the midship region of the boat.

Inside of the outer pair of rails I and 8 is an inner pair [5 and I6which, like the outer pair, converge from the opposite sides of thekeel. The inner pair of rails, however, diverge at a much smaller anglethan the outer pair, and have their rear portions extending along thehull intermediate-the keel and the outer pair, and being fairly close tothe keel. The object of this inner pair of rails is to exclude theaerated water from that area of the hull which they encompass, so as toprevent aerated water from flowing back into the propeller stream. Thus,it may be stated that the aerated water is confined to that portion ofthe hull between the inner and outer pairs of rails. The inner pair ofrails, as shown, likewise terminates adjacent the midship region of theboat.

The rails I, 8, l5 and [6 may be designated as cushion rails, for theydefine between them an area in which the hull is supported or cushionedon the aerated body of water.

A pair of rails l1 and i8 are positioned along the bottom of the hull atthe quarters, preferably arranged along the chine lines on oppositesides and extending from the stern to a point approaching the midshipregion of the hull, leaving gaps l9 and 20 of considerable width betweenthe outer rails I and 8 and the rails i1 and 18. This gap occurs wherethe pitch of the V-bottom is steepest, and the object of this gap is toprovide an avenue for the escape of the aerated water from beneath thehull. This area of the v-bottom intermediate the forward and rear guiderails constitutes an unimpeded discharge area. The rear portions of theinner rails I5 and It materially assist in directing the aerated watertoward these gaps. Thus, all of the aerated water is discharged frombeneath the hull anterior to the region of the semi-tunnel 6.

It is, of course, a matter of elemental knowl edge that the narrowingportion of any boat hull rearward of the part of greatest cross-sectioninduces a vacuum beneath and behind the boat, and if it were not for therails l1 and I8 this vacuum would draw in beneath the rear portion ofthe hull at least some of the aerated water which has been expelledthrough the gaps i9 and 20. The function of the rear rails l1 and I8,therefore, is to keep this aerated water from returning and mixing withthe water in which gardless of the speed at which the boat is driven,

thus materially advancing the maximum speed limit. a

The shape of the air cushion rails and of the rear rails, which may betermed solid water concentration rails, is a matter of option with theboat designer and builder, but I prefer to give them a stream-lineshape, as shown, so that they will oppose the minimum of resistance tothe forward movement of the boat.

While I have in the above description disclosed what I believe to be apreferred and practical embodiment of my invention, it will beunderstood that the system of rails as shown and described is applicableas well to hulls capable of entraining aerated-water atthe forefoot anddischarging it at the midship region, even though the semi-tunnelfeature may not be employed.

What I claim as my invention is:

1. In a power boat hull having a broad, sub- 2,as4,e9e

stantially flat bow overhang and forefoot, and

of v-bottom shape aft of said forefoot, a pair of deflecting railsprojecting downward from the bottom of the hull, arrangedsymmetricallywith respect to the longitudinal central line on oppositesides thereof, having their forward ends adjacent the bow above thewater line, and their rear portions adjacent the chines and terminatingadjacent the midship region at the part of the bottom having the mostpronounced V-shape,

' for guiding the aerated water churned up by the forefoot to a coursein which it will be engulfed by the forefoot and its lateral escapeprevented until it reaches the midship region, the sharply inclinedplanes of the hull immediately aft of said rails being unimpeded topermit said aerated water to escape laterally beyond the rear ends ofsaid rails.

2. Ina power boat hull as claimed in claim 1, the rear portions of saidrails being substantially parallel to the chines and lying closelyadjacent thereto.

3. In a power boat hull having a broad, substantially fiat bow overhangand forefoot, and of V-bottom shape aft of said forefoot, a plurality ofpairs of deflecting rails projecting downwardly from the bottom of thehull, arranged symmetrically with respect to the longitudinal centralline, the forward ends of the rails of each pair being adjacent the keelline, the forward ends of the outer'pair being above the water line, theouter pair of rails diverging from the keel line toward the chines andhaving their rearward portions substantially parallel to the chines,lying closely adjacent thereto and terminating adjacent the midshipregion of the hull, the inner pair of rails diverging from the keel lineand extending intermediately between the keel and chines, said inner andouter pairs of rails defining'between them a course for guiding theaerated water beneath the forefoot and along the forward portion ofthebottom of the hull, excluding that region between the rails of theinner pair, the outer pair preventing the lateral escape of the aeratedwater until it reaches the midship region of the hull, the inclinedplanes of the hull bottom immediately aft of said rails being unimpededto permit the aerated waterto escape laterally beyond the rear ends ofsaid rails. 1

4. In a propeller driven power boat hull having a broad, substantiallyflat bow overhang and forefoot, and of V-bottom shape aft of saidforefoot, a forward pair of deflecting rails projecting downwardly fromthe bottom of the hull, arranged symmetrically with respect to thelongitudinal central line on opposite sides thereof, the forward ends ofthe rails being adjacent the keel line, adjacent the bow above the waterline. and their rear portions adjacent the chines, and terminatingadjacent the midship region, for guiding the aerated water churned up bythe forefoot to a course in which it will be engulfed by the forefootand its lateral escape prevented until it reaches the midship region,and a rearward pair of rails projecting downwardly from the bottom ofthe hull on opposite sides, substantially at the chine lines along thequarters, from points adjacent the stem to points rearward of saidforward rails, leaving longitudinal unimpeded gaps between said forwardand rearward rails in the area of the V-bottom, the aerated waterrlsthus laterally diverted aerated water from bein inducted under therear portion of the hull and into the propeller path by the vacuumincident to the forward movement of the hull.

5. In a propeller driven power boat hull having a broad, substantiallyfiat bow overhang and forefoot, and of V-bottom shape aft of saidforefoot, a plurality of forward pairs of deflecting rails p ojectingdownwardly from the bottom of the hull, arranged symmetrically withrespect to .the keel longitudinal central line, the forward thereto andterminating adjacent the midship i region of the hull, the inner pair ofrails diverging from the keel line and extending intermediately betweenthe keel and chines, said inner and outer pairs of rails definingbetween them a course for guiding the aerated water beneath the forefootand along the forward portion of between the rails of the inner pair,the outer pair preventing the lateral escape of the aerated water untilit reaches the midship region of the hull, and a rearward pair of railsprojecting downwardly from the bottom of the hull on opposite sidessubstantially at the chine lines along the quarters from points adjacentthe stern to points rearward of said outer pair of forward rails,leaving unimpeded longitudinal gaps between said outer pair of forwardrails a rearward rails in that section of the hullof the sharpestV-bottom, the aerated water rising laterally along the inclined planesof the hull being P permitted to escape laterally by way of said gaps,said rearward rails preventing the thus laterally diverted aerated waterfrom being inducted un der the rear portion of the hull and into thepropeller path by the vacuum incident to the forward movement of thehull.

ANDREW J. HIGGINS.

said

